College of LAS « Illinois

Our Dynamic Brain

William Greenough showed the world that the brain is like a muscle—you use it or lose it

Preschoolers and the aged have a common ally in William Greenough.

As a biological psychologist in the Department of Psychology, Greenough investigates the nitty-gritty of how the brain forms memories—the intricate cascade of chemical and anatomical changes that result in an experience being hardwired into the brain. Scientists once believed that the structure of the brain was immutable. Its capacity to store and retrieve memories and otherwise function was considered largely predetermined by the luck of the gene pool rather than influenced by the environment. Over the past 30 years, Greenough has shown the world that the brain is as pliable as a muscle—the more a person uses it, the more versatile it becomes. And that is true for the elderly as well as the young.

"The thinking was that brain development peaked before adolescence," says Greenough. "Adults could acquire more knowledge and skill with age, but the basic machinery of their brain—its capacity to change its structure—was fixed."
Cracks in this theory of an immutable brain had appeared in the late 1960s when scientists at UC-Berkeley discovered that rats raised in "enriched environments"—that is, cages with wheels and toys that mimicked the obstacles rats would scurry around in a New York sewer—had a thicker cerebral cortex than did rats reared in traditional, sterile laboratory cages.

Greenough and two students shattered that theory in the early 1970s by measuring the characteristics of rat neurons, or nerve cells, and their synapses. Synapses are the junctures between two neurons at which the brain exchanges messages. Working in a converted dairy barn on the UI campus, Greenough, graduate student Roger West, and undergraduate Fred Volkmar showed that rats raised to rodent adolescence in enriched environments had larger neurons and more numerous synapses than those raised in sterile cages—over 20 percent more. Such a difference in brain size due to the influence of environment had never been documented before.

Greenough likes a challenge, a trait he inherited from a great-great grandmother who, in the mid-1800s, trekked 2,000 miles along the Oregon Trail. His frontier has been science, where he has consistently gone "where the questions lead."

Their work was so controversial that when the researchers submitted their results to a prominent scientific journal, it was promptly rejected. Greenough was also rejected for tenure. But his research eventually found its way into another prominent journal, and Greenough's department reconsidered its decision.

The turning point was when Greenough got similar, though less dramatic, results when his team repeated their experiments with adult rats, which showed that these effects could be attributed specifically to learning and were relatively long lasting. Like a tree sprouting more branches, the brain was forming new synapses to handle the load.

"It was a truly revolutionary moment for scientists," says Greenough, "because if the structure of the brain was changeable, it meant that anything was possible."

Among the first to recognize the significance was J. McVicker Hunt, a UI child psychologist who leaned on Greenough's research when he lobbied for the creation and expansion of the Head Start preschool program. Greenough's research was cited as empirical evidence that early enrichment could literally change the course of an underprivileged child's life.

Greenough's work also inspired programs aimed at increasing the motor skills of babies handicapped by fetal alcohol syndrome and the cognitive skills of the elderly in nursing homes. "People now talk about the brain in the context of 'use it or lose it,' even among the elderly," says Greenough. "They didn't used to do that."

Today Greenough is among the University's—and the nation's—most honored
researchers. He is a member of the National Academy of Sciences and has received the Distinguished Scientific Contribution award from the American Psychological Association and the William James Award from the American Psychological Society, among others. Subsequent investigations, by Greenough's teams and others have shown that most of brain tissue, not just nerve cells, change as a result of experiences. Recently his team, led by long-time colleague Ivan Jeanne Weiler, an adjunct associate professor of psychology, discovered a key step in understanding the cause of a common inherited form of mental retardation called fragile X—another first.